# Lists what is in the current location.
[arcc-t05@blog1 ~]$ ls
Desktop  Documents  Downloads

# Throws an error.
[arcc-t05@blog1 ~]$ LS
-bash: LS: command not found
Filename  ≠  FiLeNaMe  ≠  FILENAME

[arcc-t05@blog1 ~]$ man ls
LS(1)                                     User Commands                                     LS(1)
NAME
       ls - list directory contents
SYNOPSIS
       ls [OPTION]... [FILE]...
DESCRIPTION
       List  information about the FILEs (the current directory by default).  Sort entries alpha‐
       betically if none of -cftuvSUX nor --sort is specified.
       Mandatory arguments to long options are mandatory for short options too.
       -a, --all
              do not ignore entries starting with .
       -A, --almost-all
              do not list implied . and ..
       ...
Manual page ls(1) line 1 (press h for help or q to quit)

[arcc-t05@blog1 ~]$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
      --author               with -l, print the author of each file
  -b, --escape               print C-style escapes for nongraphic characters
      --block-size=SIZE      with -l, scale sizes by SIZE when printing them;
                               e.g., '--block-size=M'; see SIZE format below
  -B, --ignore-backups       do not list implied entries ending with ~

[arcc-t05@blog1 ~]$ ls -al ~

[arcc-t05@blog1 ~]$ ls \
> -al \
> ~

[arcc-t05@blog1 ~]$ ls
Desktop  Documents  Downloads

[arcc-t05@blog1 ~]$ ls -al
total 76
drwxr-x---   8 arcc-t05 arcc-t05  4096 Oct  3 13:57 .
drwxr-xr-x 925 root     root     32768 Sep 27 16:21 ..
-rw-------   1 arcc-t05 arcc-t05   212 Sep 12 15:44 .bash_history
-rw-r--r--   1 arcc-t05 arcc-t05    18 Aug 10 17:00 .bash_logout
-rw-r--r--   1 arcc-t05 arcc-t05   141 Aug 10 17:00 .bash_profile
-rw-r--r--   1 arcc-t05 arcc-t05   376 Aug 10 17:00 .bashrc
drwx------   3 arcc-t05 arcc-t05  4096 Sep 12 11:36 .config
drwxr-xr-x   2 arcc-t05 arcc-t05  4096 Aug 10 17:00 Desktop
drwxr-xr-x   2 arcc-t05 arcc-t05  4096 Aug 10 17:00 Documents

# Reset: Type the following:
[arcc-t05@blog1 ???]$ cd

[arcc-t05@blog1 ~]$
# The ~ “tilda” character represents your home directory.

[arcc-t05@blog1 ~]$ pwd
/home/arcc-t05

# Reset: cd
# Move up one level.
# Move into the folder’s parent.
[arcc-t05@blog1 ~]$ cd ..
[arcc-t05@blog1 ~]$ pwd
/home

[arcc-t05@blog1 home]$ cd ..
[arcc-t05@blog1 /]$ pwd
/
# In the ‘root’ folder
[arcc-t05@blog1 /]$ ls

# Are we defining an absolute or relative path?
[arcc-t05@blog1 /]$ cd opt
[arcc-t05@blog1 opt]$ pwd
/opt

[arcc-t05@blog1 opt]$ cd
[arcc-t05@blog1 ~]$

# Are we defining an absolute or relative path?
[arcc-t05@blog1 ~]$ cd /usr/include/asm
[arcc-t05@blog1 asm]$ pwd
/usr/include/asm

[arcc-t05@blog1 asm]$ cd ../..
[arcc-t05@blog1 usr]$ pwd
/usr

[arcc-t05@blog1 usr]$ cd
[arcc-t05@blog1 ~]

# Reset: cd
# List files in the user’s home folder.
[arcc-t05@blog1 ~]$ ls

# List long format that includes ownership and permission details.
[arcc-t05@blog1 ~]$ ls -l

# List all files, including hidden files and folders start with “.”.
[arcc-t05@blog1 ~]$ ls –a

# Notice how ‘short-name’ options are grouped.
# List all files with long format.
[arcc-t05@blog1 ~]$ ls –al

# List all files with long format, in reverse order.
[arcc-t05@blog1 ~]$ ls –alr

# List all files with long format, in reverse order, in human readable form.
[arcc-t05@blog1 ~]$ ls –alrh

$ cd
[~]$ ls
Desktop  Documents  Downloads

[~]$ mkdir folder01
[~]$ ls
Desktop  Documents  Downloads  folder01

[~]$ mkdir folder01
mkdir: cannot create directory ‘folder01’: File exists

[~]$ cd folder01/
[folder01]$ pwd
/home/arcc-t05/folder01

[folder01]$ mkdir folder02
[folder01]$ ls
folder02

[folder01]$ cd folder02/
[folder02]$ pwd
/home/arcc-t05/folder01/folder02

[folder02]$ cd ../..
[~]$ pwd
/home/arcc-t05

$ cd
# Create an empty file.
[~]$ touch myfil.txt
[~]$ ls
Desktop  Documents  Downloads  folder01  myfil.txt

# Rename the file ‘myfil.txt’ to ‘myfile.txt’:
[~]$ mv myfil.txt myfile.txt 
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile.txt

# Move the file ‘myfile.txt’ into the directory ‘folder01’
[~]$ mv myfile.txt folder01/

[~]$ ls
Desktop  Documents  Downloads  folder01

# We can ‘ls’ what is in a relative folder.
[~]$ ls folder01/
folder02  myfile.txt

$ cd
# Use the touch command to create an empty file.
[~]$ touch myfile02.txt
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02.txt

# Copy (duplicate) a file.
[~]$ cp myfile02.txt myfile02b.txt 
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02b.txt  myfile02.txt

# Copy a file into an existing folder.
[~]$ cp myfile02b.txt folder01/
[~]$ ls folder01/
folder02  myfile02b.txt  myfile.txt

[~]$ cp folder01
cp: missing destination file operand after 'folder01'
Try 'cp --help' for more information.

[~]$ ls folder01
folder02  myfile02b.txt  myfile.txt

[~]$ cp folder01 folder03
cp: -r not specified; omitting directory 'folder01’

# “recursively” copy a folder and all its contents.
[~]$ cp –r folder01 folder03
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03 myfile02b.txt  myfile02.txt

[~]$ ls folder03
folder02  myfile02b.txt  myfile.txt

[~]$ ls 
Desktop  Documents  Downloads  folder01  folder03  myfile02b.txt  myfile02.txt

[~]$ mkdir folder04
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03  folder04  myfile02b.txt  
myfile02.txt

# Can remove folder04 since it is empty.
[~]$ rmdir folder04
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03  myfile02b.txt  myfile02.txt

[~]$ rmdir folder03/
rmdir: failed to remove 'folder03/': Directory not empty

[~]$ cd
[~]$ cd folder03
[folder03]$ ls
folder02  myfile02b.txt  myfile.txt
[folder03]$ ls folder02/
[folder03]$

# ‘folder02’ is empty.
[folder03]$ rmdir folder02/
[folder03]$ ls
myfile02b.txt  myfile.txt

[folder03]$ rm myfile.txt 
[folder03]$ ls
myfile02b.txt

[folder03]$ rm myfile02b.txt

[folder03]$ ls
[folder03]$
# ‘folder03’ is now empty.

[folder03]$ cd ..
[~]$ rmdir folder03/
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02b.txt  myfile02.txt


# This has taken a lot of individual steps.
# Can we do this quicker?

[~]$ cd
[~]$ rm folder01/
rm: cannot remove 'folder01/': Is a directory

[~]$ rm --help
Usage: rm [OPTION]... [FILE]...
Remove (unlink) the FILE(s).
...
  -r, -R, --recursive   remove directories and their contents recursively
...

[~]$ rm -r folder01/
[~]$ ls
Desktop  Documents  Downloads  myfile02b.txt  myfile02.txt

# Can remove multiple files.
[~]$ rm myfile02b.txt myfile02.txt 
[~]$ ls
Desktop  Documents  Downloads

[~]$ history --help
history: history [-c] [-d offset] [n] or history -anrw [filename] or history -ps arg [arg...]
    Display or manipulate the history list.
    ...

[~]$ history 
  ...	
  219  rm -f folder01/
  220  rm -r folder01/
  221  ls
  222  rm myfile02b.txt myfile02.txt 
  223  ls
  224  history

# Repeat command ‘223’
[arcc-t05@blog1 ~]$ !223
ls
Desktop  Documents  Downloads

[]$ man ls
-R, --recursive
              list subdirectories recursively

[]$ ls -R

[arcc-t05@blog1 ~]$ cd /project/arccanetrain/intro_to_linux
[arcc-t05@blog1 intro_to_linux]$ ls -al
total 54
drwxrwsr-x  4 salexan5 arccanetrain  4096 Oct  6 08:09 .
drwxrws--- 40 root     arccanetrain  4096 Oct  6 08:09 ..
drwxrwsr-x  2 salexan5 arccanetrain  4096 Oct  5 11:19 clusters
drwxrwsr-x  6 salexan5 arccanetrain  4096 Oct  5 14:56 data
-rw-rw-r--  1 salexan5 arccanetrain   874 Oct  5 15:30 fruits.txt
-rw-rw-r--  1 salexan5 arccanetrain 34472 Oct  5 10:57 software.csv
-rw-rw-r--  1 salexan5 arccanetrain  1603 Oct  6 08:08 vegatables.txt
-rw-rw-r--  1 arcc-t05 arccanetrain    26 Oct  5 07:20 workshop_all.txt
-rw-------  1 arcc-t05 arccanetrain    23 Oct  5 07:20 workshop_me.txt

drwxrwsr-x    clusters          # A folder.
-rw-rw-r--    workshop_all.txt  # A file.

-rw-rw-r--    1 arcc-t05 arccanetrain     26 Oct  5 07:20 workshop_all.txt

[]$ cd /project/arccanetrain/
# drwxr-sr-x    2 arcc-t01 arccanetrain   4096 May 16 16:26 arcc-t01
# No one other than arcc-t01 has permission to write within this folder.
[arccanetrain]$ cd arcc-t01/

# Can arc-t05 create (write) a file within this folder?
[arcc-t01]$ touch text.txt
touch: cannot touch 'text.txt': Permission denied

[arcc-t01]$ cd ../intro_to_linux
# -rw-rw-r--    1 arcc-t05 arccanetrain     26 Oct  5 07:20 workshop_all.txt
# Anyone within the group can read/write this file.
[intro_to_linux]$ cat workshop_all.txt
Everybody can read this.

# Only arcc-t05 can read/write this file.
# -rw-------    1 arcc-t05 arccanetrain     23 Oct  5 07:20 workshop_me.txt
[intro_to_linux]$ cat workshop_me.txt
cat: workshop_me.txt: Permission denied

[]$ cd /project/arccanetrain/
[arccanetrain]$ cd arcc-t05

[arcc-t05]$ touch test.txt
# Do you get a “Permission denied”?

# Navigate into the intro_to_linux folder. 
[arcc-t05]$ cd ../intro_to_linux

[intro_to_linux]$ cat workshop_all.txt
Everybody can read this.

[intro_to_linux]$ cat workshop_me.txt
# Do you get a “Permission denied”?
# Can you cd into the /opt folder?
# Justify your answer.
# Can you cd into the /root folder?
# Justify your answer.

# Can you cd into the /opt folder?
[arcc-t05@blog1 ~]$ cd /opt
[arcc-t05@blog1 opt]$

# Can you cd into the /root folder?
[arcc-t05@blog1 ~]$ cd /root
-bash: cd: /root: Permission denied

# Justify your answer.
[arcc-t05@blog1 ~]$ ls -l /
...
# “other” has read permissions
drwxr-xr-x.    5 root root    43 Jun 26 11:47 opt
...
# No permission set for other read permissions
dr-xr-x---.   17 root root  4096 Oct  4 12:58 root